Barrel-feed mechanism



June 19, 1962 l. R. BARR 3,039,364

BARREL-FEED MECHANISM Filed May 3, 1960 2 Sheets-Sheet 1 IRWIN R BARR HSFIG. 4 BY J- ATTORNEY 2 Sheets-Sheet 2 Filed May 3. 1960 [I'll Ill INVENTOR.

IRWIN R. BARR ATTORNEY United States Patent Office 3,39,354 Patented June 19, 1962 3,039,364 BARREL-FEED NECHANISM Irwin R. Barr, Baltimore County, Md, assignor to Aircraft Armaments, lnc., Cockeysville, Md., a corporation of Maryland Filed May 3, 1960, Ser. No. 26,568 Claims. (Cl. 8933) This invention relates to machine guns of the type firing cartridges that are linked together in belt form, and more particularly, to a feed mechanism for indexing cartridges into a position where they can be stripped from the belt and inserted in the gun chamber and fired, and an ejector mechanism for ejecting cartridges from the gun after they are extracted from the chamber.

Ammunition for guns of the class described is in the form of long belts of cartridges linked together. In operating such guns, it is necessary to index the belt each time the gun is fired so as to place a new cartridge in a position where it can be stripped from the belt and inserted into the gun chamber. In guns of the class described, recoil movement of the bolt is usually employed to operate a feed mechanism which indexes the belt each time the gun is fired. The necessity for utilizing the energy of the recoiling bolt to move a long, heavy belt of ammunition creates a problem when it is desired to obtain a very rapid rate of fire from the gun. Because the rate at which the bolt recoils determines the time interval between firings, it is obvious that any factor which causes a large portion of the recoiling energy of the bolt to be used for a purpose other than'accelerating the recoil of the bolt will decrease the rate of fire. In other words, with high belt loads arising from long belts that are twisted, the bolts of guns of the class described are slowed considerably during recoil thereby seriously affecting the rate of fire of such guns. One solution to this problem is to employ auxiliary ammunition boosters which are electric motors that feed the belted ammunition into the gun thereby reducing the belt loads required to be handled by the recoiling bolt. The deficiency of this approach is in the complexity of equipment ancillary to the gun itself and the power required to run such equipment.

,It is therefore a primary object of this invention to provide, for a machine gun of the class described, a feed mechanism which achieves positive belt indexing without using any of the recoil energy of the bolt and without requiring auxiliary ammunition boosters.

As a feature of this invention whereby the primary object is achieved, energy to pivot a feed arm connecting with an indexing mechanism is extracted from the recoiling barrel.

Werethe recoiling barrel to operate directly upon the feed arm, the sudden impulse applied thereto i '1 .would be transmitted to the belt in such a manner that the inertia of the latter would cause the links of the belt to fail. This is prevented by interposing resilient means between the recoiling barrel and the feed arm such that the initial shock of the recoiling barrel is absorbed and applied more gradually to the feed arm. To facilitate hand chargingyof .the, gun, the feed arm is mounted on the receiver so that to index the belt, the arm is pivoted from a pos tion in the path traversed by the bolt during its recoil to a position outof such path. The geometry of the construction provides for barrel recoil to pivot the feed arm out .of the path of the recoiling bolt before its contact therecomplished by using the recoiling bolt to pivot a lever into engagement with the extracted cartridge. Such engageon rails 18.

ment flips the extracted cartridge out of the receiver. Only a small amount of enery is extracted from the recoiling bolt in this manner so that there is no significant decrease in the firing rate of the gun.

The more important features of this invention have thus been outlined rather broadly in order that the detailed description thereof that follows may be better understood, and in order that the contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will also form the subject of the claims appended hereto. Those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other structures for carrying out the several purposes of this invention. It is important, therefore, that the claims to be granted herein shall be of suflicient breadth to prevent the appropriation of this invention by those skilled in the art.

In the drawing:

FIGURE 1 is a sectional view of a machine gun into which the invention has been incorporated.

FIGURE 2 is a top view of the gun shown in FIGURE 1 with the top part of the receiver removed to facilitate showing the invention.

FIGURE 3 is similar to FIGURE 2 but shows the various positions of the gun elements after the bolt has recoiled and the barrel extension is returning to battery position.

FIGURE -4 is a sectional view taken along the line 4- 4 of FIGURE 2.

FIGURE 5 is a side view of the feeder-ejector mechanism which forms the basis of this invention.

FIGURE 6 is a top view of the mechanism shown in FIGURE 5 with various parts removed to facilitate an understanding of the construction.

FIGURE 7 is a sectional view of the mechanism.

Referring now to FIGURE 1, reference numeral 10 designates generally a machine gun having a hollow receiver 11 with a forward portion 12, an intermediate portion 13, and a rearward portion 14. Portion 12 has cylindrical bearing ring 15 into which the bearing '16 of barrel 17 is slideably mounted to effect barrel movement between battery and recoil positions. Each side of portion 13 of receiver 11 is provided with longitudinally extending guide rails 18 which support barrel extension 19 and permit the same to reciprocate in the receiver. Barrel extension '19 has a forward end which interlocks with the breech portion of barrel 17 adjacent chamber 20 to define a barrel as sembly. Barrel extension 15! also has rearwardly extending legs 21 which have longitudinal grooves therein riding In this manner, the barrel assembly comprising barrel 17 and barrel extension 19 moves in receiver 11 as a unit supported by rails 18 and bearing ring 15.

The rearmost portion of each leg 21 is axially bored as shown in FIGURE 4 for the reception of barrel extension buffer 2.2 containing a compression spring. Buffer 22 abuts end plate 23 on portion '14 of the receiver such that the barrel assembly is constantly urged toward battery position as shown in FIGURE 1.

Accelerator 24 is U-shaped. The legs are pivotally mounted on the receiver and straddle barrel '17. Connector portion 25 is beneath the barrel and is urged into engagement with the rear face of bearing 16 by a spring (not shown). 7 V

Slideably mounted on barrel extension "19 is bolt assembly 26 which includesbolt block 27 and bolt slide 28. Bolt slide 28 ha a plate-like portion 29 which is slideably engaged in grooves 35 formed in the inner faces 31 of legs 21. Integrally beneath the portion 2 9 is buffer cylinder 32 having a bore 33 which is engageable over buffer spring 34 which itself is mounted at the rear of receiver 1. Cylinder 32 has an aperture in the center thereof through 3 which shaft 35 passes. Barrel return spring 36 mounted on shaft 35 has one end bearing on the rear of receiver 11 and the other end bearing on cylinder 32 as shown in FIG- URE 1. The rear portion 37 of bolt slide 28 projects upwardly between faces 31 and has firing pin 33 rigidly attached thereto facing toward the forward end of the re ceiver. Through the center of portion 37 is axial slot 39.

Bolt block 27 has a rearward guide portion 40 slideably engaged in slot 39. To limit relative movement between block 27 and slide 2%, portion 46 is slotted as at 41 and pin 42 passing through slot 41 is rigidly connected to rear portion 37 of slide 28. Block 27 has a forward face 54) which fits flush against a cartridge base. Aperture 43 in face 50 permits firing pin 38 to project beyond face 50 when the bolt assembly is positioned on the barrel assembly at the forward most position of the bolt assembly adjacent chamber 20. Pivotally attached to bolt block 27 are bolt locks 44 which are engageable with faces 31 of legs 21 when the bolt assembly is at any position on the barrel assembly remote from the chamber (see FIGURE 3). As barrel return spring 36 drives bolt assembly 26 from its position remote from chamber 20' toward the chamber, pin 41 is at the rear of slot 41 and firing pin 38 is internal to aperture 43 and does not project beyond face 50. Locks 44 bear against faces 31 and preclude relative movement between bolt slide 28 and bolt block 27 during travel of the bolt assembly toward the chamber. Stripper 45 projects above block 27 and during such travel passes through slot 46 in ammunition tray 4-7 which is above and behind chamber 20. Links 43 are slideable on tray 47 in a direction normal to the direction of bolt travel. During the counter-recoil stroke of the bolt assembly, stripper 45 engages the base of a cartridge held by link 48 and strips the cartridge from the link. Chambering ramp 49 cams the nose of the cartridge downwardly into chamber 20 as the bolt assembly moves toward the chamber. Eventually surface 50 engages the base of the cartridge and rams the same into the chamber, whereupon movement of block 27' halts. However, movement of slide 28 continues as rear portion 37 cams locks 44 into keepers 51 formed in the sides of barrel extension 19. Simultaneously with pivotal movement of the locks into keepers '1, firing pin 38 slides in aperture 43 and projects beyond face 50 contacting the primer in the base of the cartridge. Thus, movement of the bolt assembly to its forwardmost position simultaneously locks the bolt assembly to the barrel extension and fires the cartridge in the chamber. FIGURE 1 shows the position of the various parts at the instant the gun is fired.

Upon firing of the cartridge, the barrel assembly and bolt assembly begin to recoil together. Recoil movement of bearing 16 causes accelerator 24 to pivot, but the geometry of the accelerator is such that connector 25 moves at the same linear velocity as the bolt assembly during initial recoil movement. This permits the gas pressure in the barrel to decrease before the bolt assembly is unlocked from the barrel extension. As the recoil movement of the barrel assembly continues, accelerator 24 pivots further causing bolt slide 28 to move relative to the barrel extension. Such relative movement causes pin 4-2 to slide in slot 41 and locks 44 are oammed out of keepers 51. Further recoil of the barrel assembly causes accelerator 24 to accelerate the bolt assembly toward its position shown in FIGURE 3. Recoil of the barrel assembly is halted by buffer 2 2 whose spring returns the barrel assembly to battery position while the bolt assembly is still recoiling on the barrel extension.

Bottom extractor 52 is pivotally mounted on bolt block 27 and by means of cam groove 53 is caused to be engaged with the rim of a cartridge as the latter is chambered. Side extractor 54- is also engaged with the rim during chambering. In this manner, extractors 52 and 54 operate on the rim of a cartridge to extract the same. from the chamber during recoil movement of the bolt assembly on the barrel extension.

Recoil of the bolt assembly on the barrel extension is halted by buffer spring 34 acting on cylinder 32. Just prior to buffering, the cartridge extracted by extractors 52 and 54 is ejected from the receiver. After bufiering, barrel return spring 36 drives the bolt assembly forward on its counter-recoil stroke. The sequence of stripping a cartridge from the belt, chambering the stripped cartridge, firing and extracting the cartridge is again repeated until sear 55 is pivoted into engagement with rear portion 37 of the bolt assembly. When this occurs upon the release of trigger 56, the bolt assembly is prevented from finishing its counter-recoil stroke.

Apertured ears 57 project from each side of portion 13 of receiver 11 and surround ammunition slits 5 8. For right-handed feed, ammunition tray 47 is attached to the pair of ears above slit 5 8 on the left side of the receiver. A feeder ejector mechanism 60 is attached to the four ears on the right side of the receiver. Above tray 47 is mounted ratchet feed mechanism 61, which includes slider 62 mounted in tracks 63 on receiver 11 so as to be movable in a direction parallel to the direction in which the linked ammunition is fed into the receiver. Facing links 48, slider 62 has lugs rigidly supporting pivot pin 64 upon which ratchet arm 65 is pivotal. Ratchet arm spring 66 resiliently urges the free end of arm 65 away from the slider as shown in FIGURE 4. The free end of arm 65 has cam edge 67 which is engageable with links 48. Spring housing 68 is detachably connected to tracks '63, and for right-handed feed is positioned at the extreme left of tracks 63. Housing 68 is centrally apertured at 69 to receive ratchet spring 70 having one end bearing on housing 68 fixed to the receiver and the other end bearing on slider 62 for constantly urging the slider away from the housing. When slider 62 is furthest from housing 68, ratchet arm 65 is positioned so that cam edge 67 is engaged with a link on the cartridge belt that is adjacent opening 46. Movement of slider 62 toward housing 68 causes edge 67 to move the link into alignment with opening 46. Further movement of slider 62 away from housing 68 results in the next link in the belt camming arm 65 toward slider 62 against the action of spring 66 until the slider is furthest from the housing. At this point, spring 66 moves edge 67 into engagement with the next link preparatory to moving the same over slot 46. In this manner, oscillatory movement of slider 62 causes indexing of the belt.

The actuation of slider 62 in a manner timed to firing of the gun is achieved by feeder-ejector mechanism 60, which includes barrel feed support 71, housing assembly 72 slideably mounted on support 71, feed arm 73 and ejector arm 74. Barrel feed support 71 has a body 71' that is generally square in cross-section and elongated. Apertured connected ears 75 are provided at the remote ends of body 71' for mating with ears 57 on the receiver.

Projections 76 extend away from body 71' and bear against the sides of receiver 11 when removable connectors 78 are inserted in the mating apertures of cars 57 and 75. In this manner, support 71 is securely fixed to the receiver.

Body 71 is provided with upper and lower longitudinally extending apertures 77 in which removable rod 78 can be inserted. A pair of transverse slots 79 are formed in the upper and lower surfaces of body 71'. A single blind hole 80 is provided in body 71' opening into the upper slots 79 and a single blind hole 80' is provided in body 71' opening into the lower slots 79. Holes 80 and 80' are adjacent. Link-engaging fingers 81 are pivotally mounted in upper slots 79 on rod 78. The free end of each finger is biased away from body 71' by a spring 82 which is inserted in blind hole 80.

The forward portion of body 71' contains centrally located dovetail groove 81 which extends longitudinally. The rearward portion of body 71 has a triangular recess 82 therein with an aperture 83 at an apex of recess 82. Projecting beyond body 71 is apertured boss 84. The

rear end of body 71' is recessed at 85. With this construction, support 71 can be attached to either the right side of the receiver for right-hand feed or to the left side of the receiver for left-hand feed. Removal of rod 78 from one aperture 77 and insertion into the other aperture 77 permits fingers 8 1 to properly engage the links in the cartridge belt when the latter is fed from either side of the receiver. Thus, while a right-hand feed is shown in the drawing, the disclosed construction permits the gun to be changed to left-hand feed merely by rotating body 71' through 180 and attaching the same to the left side of the receiver.

Housing assembly 72 includes elongated housing 86 having rib 87 along one edge that is slideably engaged in dovetail groove 81 on body 71. Housing 86 has a cylindrical bore 88 therein extending rearwardly from a closed end adjacent the forward end of body 71. Slideable in the open end of housing 86 is plunger 89. Pin 90 is rigidly attached to plunger 89 and is slideable in slots 91 formed in housing 86 to limit relative movement of plunger 89 in the housing. Plunger 89 is urged toward the open end of housing 86 by spring 92 which bears against the closed end of the housing and against a shoulder 93 on plunger 89. Plunger 89 also has head 94 which projects beyond the open end of housing 86.

Feed arm 73 is a bell-crank having one end pivotally mounted on pin 95 in recess 82. Cam face 96 is caused to abut plunger head 94 by the action of spring 97. The free end of arm 73 contains cam slot 98. Adjacent slot 93 'is cam portion 99. As shown in FIGURE 1, slot 93 is engaged by the free end 100 of actuator crank 101. Crank 101 is pivotally attached to the top of receiver 11 by pin 102. On the end of crank 101, opposite to end 100, is a lever arm 103 engaged in notch 104 in slider 62.

Ejector arm 74 is bifurcated and has forward web 104 and rearward web 105 interconnecting arms 106. Arm 74 is pivotally connected to body 71 by pin 107 attached to boss 84. Spring 108 acting between body 71 and rear web 105 biases arm 74 in the clockwise direction as seen in FIGURE 6. In normal position, web 104 acting on housing 86 retains arm 74 just out of the path of movement of the bolt assembly when the latter recoils on the barrel extension. The rear portion of arms 106 project outwardly at 109 into the path of movement of the bolt assembly when arm 74 is in normal position.

Spring 70 is strong enough to urge slider 62 to the far side of the receiver and position lever 103 such that end 100 of crank 101 retains feed arm 73 in the position shown in FIGURE 2. In such position, arm 73 extends into the path traversed by bolt assembly 26 when the latter recoils on the barrel assembly. FIGURES l and 2 show the relative positions of the barrel assembly, bolt assembly and feed arm at the instant the gun is fired. The closed end of housing 86 abuts one edge 110 of barrel extension 19 when the gun is fired. As above described, the barrel assembly and bolt assembly initially recoil as a unit. Such initial recoil imparts rearward movement to housing 86 without causing plunger 89 to move. After pivoting movement of accelerator 24 causes the bolt assembly to be unlocked from the barrel assembly, the bolt assembly begins its recoil movement on the barrel assembly and travels toward arm 73. Meanwhile, the recoil of the barrel assembly compresses spring 92 to a solid condition. Spring 92 at this time has absorbed the initial shock of the recoiling barrel assembly and begins to cause plunger 89 to move rearwardly. Head 94 acting on cam face 96 of arm 73 causes the latter to pivot about pin 95 from its position in the path traversed by the bolt assembly (FIGURE 2) to its position out of the path of the bolt assembly (FIGURE 3). The geometry is such that plunger 89 acts prior to the time that the recoiling bolt assembly would contact cam portion 99 on arm 73. As arm 73 pivots out of the path of the bolt assembly, the latter strikes projection 109 causing ejector arm 74 to pivot about pin 107. The

pivotal movement of arm 74 causes web 104 to strike the cartridge extracted by the bolt assembly forward of side extractor 54. The sharpness of this blow causes the extracted cartridge to pivot about the side extractor. The momentum of the extracted cartridge then causes the same to be flipped through opening 57 in the receiver. FIGURE 3 illustrates the relative positions or" the various elements as the bolt assembly is buffered and just before the barrel assembly returns to battery position.

As above described, the pivotal movement of feed arm 73 causes slider 62 to index the belted ammunition and place a new round above slot 46 in the ammunition tray. FIGURE 4 shows the position of the slider corresponding to the position of the feed arm shown in FIGURE 3. As the bolt driving spring moves the bolt assembly through its counter-recoil stroke and stripper 45 strips a new round from the links held in the ammunition tray, spring 70 assisted by spring 97 returns arm 73 to its normal position in the path of the bolt assembly as ratchet 65 is returned to its position ready to again index the belt. Spring 108 also returns ejector arm 74 to its normal position so that after the stripped round is fired, the abovedescribed sequence of events will again occur. Spring 92. also returns housing 86 to its normal position abutting portion on the barrel extension. Fingers 81 prevent overrunning of the belt during indexing.

The lower portion of receiver 11 is slotted as at along the path traversed by the bolt assembly when the latter recoils. Such slots provide clearance for a pin that can be rigidly connected to either side of cylinder 32 of the bolt assembly. A plunger 116 is slideably mounted in a tube 117 laterally of slot 115. Plunger 116 is urged to a position forward of the pin in cylinder 32 so that there is no contact with plunger 116 while the gun is firing and the bolt assembly is moving. In the event that a round fails to fire, the gun can be handcharged by manually pulling plunger 116 rearwardly. Rearward movement of plunger 116 imparts rearward movement to the bolt assembly through the pin in cylinder 32. Since the barrel assembly remains stationary during hand charging, the bolt assembly contacts cam portion 99 on arm 73 causing the latter to pivot and index the belt. The bolt assembly also contacts projection 109 and causes arm 74 to pivot thereby ejecting the defective round. If trigger 56 is depressed, release of plunger permits the bolt return spring to drive the bolt assembly forward stripping another round from the belt. Firing again commences.

, Those skilled in the art can now appreciate that this invention permits the recoiling barrel to index the belt without affecting the time required for the bolt assembly to traverse its recoil and counter-recoil displacement. In addition, the shock of the recoiling barrel is absorbed prior to indexing the belt so that shock loading of the belt does not occur. By the above-described novel arrangement, hand charging of the gun can also easily be carried out utilizing the same components.

What is claimed is:

1. In a machine gun for firing cartridges that are fed to the gun linked together, the combination of a receiver, a barrel assembly slideably mounted in said receiver for reciprocation between battery and recoil positions, a chamber in said barrel assembly for holding a cartridge, a bolt assembly slideably mounted on said barrel assembly for reciprocation thereon between a first terminal position adjacent said chamber where a cartridge in the chamber is fired and a second terminal position remote from the chamber where a cartridge extracted from the chamber can be ejected from the receiver, actuatable ratchet feed means, actuation of said feed means indexing linked cartridges into the receiver, a feed arm having one end pivoted relative to the receiver, the other end of said feed arm being engaged with said ratchet feed means, spring means for releasably maintaining said feed arm in the path traversed by the bolt assembly when the latter moves from its first to its second terminal position, said feed arm being pivotal out of the path of said bolt assembly for actuating said ratchet feed means, firing of a cartridge in the chamber causing said barrel assembly to move from battery to recoil position, movement of said barrel assembly toward recoil position causing said bolt assembly to move from its first to its second terminal position, and means repsonsive to movement of the barrel assembly toward recoil position for pivoting said feed arm out of the path of said bolt assembly before the latter contacts the feed arm.

2. In the machine gunof claim 1 wherein said bolt assembly extracts a cartridge from the chamber when said bolt assembly moves to its second terminal position,

an ejector arm pivotally mounted on said receiver, and an ejector spring urging said ejector arm into the path traversed by the bolt assembly when the latter moves from its first to its second terminal position, :movement of said bolt assembly to its second terminal position causing it to strike said ejector arm and cause the latter to pivot and engage the extracted cartridge whereby the latter is ejected from the receiver.

3. The combination of claim 1 wherein said bolt assembly has means for manually moving the'same on the barrel assembly from the first terminal position of the bolt assembly to the second terminal position whereby the feed arm is engaged and caused to pivot formanually actuating the ratchet feed means independently of move-- ment of the barrel assembly.

4. In a machine gun for firing cartridges that are feed to the gun linked together, the combination of a receiver, a barrel assembly slideably mounted in said receiver for reciprocation between battery and recoil positions, a chamber in said barrel assembly for holding a cartridge,

a bolt assembly slideably mounted on said barrel assembly for reciprocation thereon between a first terminal position adjacent said chamber Where a cartridge in the chamber is fired to a second terminal position remote from the chamber where a cartridge extracted from thechamber can be ejected from the receiver, actuatable ratchet feed means, actuation of said feed means causing the linked cartridges to be indexed into the receiver, a feed arm having one end pivoted relative to the receiver, the other end of said feed arm being engaged with said ratchet feed means, resilientmeans for releasably maintaining said feed arm in the path traversed by. the bolt assembly when the latter moves from its first to its second terminal position, said feed arm being pivotal out of the path of said bolt assembly for actuating said ratchet feed means, firing of a cartridge in the chamber causing said barrel assembly to move from battery to recoil position, movement of said barrel assembly toward recoil position causing said bolt assembly to move from its, first to its second terminal position, a housing slideably mounted on said receiver, said barrel assembly having a portion engageable with said housing when saidbarrel assembly moves toward recoil position for moving said housing, and resilient means interposed between said housing an: said feed arm, movement of said barrel assembly toward recoil position causing said portion thereon to strike said housing and move the same, said last named resilient means absorbing the impact energy of said portion on said housing, the impact energy absorbed by said last named resilient means being effective to pivot said feed arm out of the path of said bolt assernbly before the latter contacts the feed arm.

5. The combination of claim 4 wherein movement of said bolt assembly to its second terminal position extracts the fired cartridge from the chamber, said machine gun having an ejector arm pivotally mounted on. said receiver, and means for resiliently urging said ejector arm into the path traversed by the bolt assembly when the latter moves from its first to its second terminal position, movement of said bolt assemblyto its second terminal position causing it to strike said ejector arm and cause the latter to pivot and engage the fired cartridge for ejecting the same from the receiver.

Johnson Oct. 20, 1953 Friend et al. Feb. 4, 1958 

